Brazilian police and striking subway workers have clashed in a central Sao Paulo commuter station, with union officials threatening to maintain the work stoppage through the World Cup opening match this week.

Brazilian police and striking subway workers have clashed in a central Sao Paulo commuter station, with union officials threatening to maintain the work stoppage through the World Cup opening match this week.

Authorities are deeply worried about the strike because the subway is the main means of transportation for World Cup fans scheduled to attend Thursday's opening match when Brazil take on Croatia. The stadium is about 20 kilometres (12 miles) east of central Sao Paulo, where most tourists stay.

Riot police firing tear gas pushed about 100 striking workers out of the station as the strike threw Sao Paulo's normally congested traffic into chaos for a fifth day. About half of the city's subway stations were operating, but with greatly diminished service.

"This is the way they negotiate, with tear gas and repression," said Alexandre Roland, a union leader, as he and others regrouped outside the station after confronting riot police.

The striking workers marched towards the city centre, where they planned to join a wide-ranging rally by various activist groups, including homeless workers demanding low-cost housing and a group calling for free public transportation.

Mr Roland said the strike will continue through the tournament opener unless the government meets workers' demands for a pay increase of just over 12%. A Sao Paulo labour court over the weekend fined the union 175,000 dollars (£104,137) for the first four days of the strike and said it would add 220,000 dollars (£130,915) for each additional day the work stoppage continued.

So far, the government-controlled company that runs the subways is offering an 8% increase, and says it cannot go higher because fares have not been raised for two years.

Last year, a fare increase was reversed after violent protests broke out.

The standoff with the Sao Paulo transport workers is the latest unrest to hit Brazil in the run-up to the World Cup. Teachers remain on strike in Rio de Janeiro and routinely rally and block streets. Police in several cities have gone on strike, but are back at work now.

The work stoppages are in addition to a steady drumbeat of anti-government protests that began a year ago during massive rallies in scores of Brazilian cities. Those protests blasted government spending for the World Cup and demanded big improvements in woeful public services such as hospitals, schools, security and transportation.

The protests have greatly diminished in size but not in frequency. Demonstrations have repeatedly erupted in Brazil's metro areas in recent months, with even a small number of protesters blocking main roads and severely disrupting traffic.